Process for making sheets with parallel pores of uniform size

ABSTRACT

Processes for making sheets with parallel pores of uniform size are described. In one form, the process comprises the steps of: extruding a slurry formed of short, non-metallic filament pieces, a metal powder, water and a plasticizer through a suitable orifice to align the filament pieces parallel to one another; cutting the extrusion into suitable sections; stacking the sections in parallel in a refractory container; compacting the stack; heating the stack in a reducing atmosphere; compacting while hot, if necessary; slicing, at right angles to the longitudinal axis of the original sections, the thusly formed billet into sheets; and, leaching out the filament pieces in each sheet. In an alternate form, a continuous filament, as opposed to short filament pieces, is used. In addition, the continuous filament is drawn through a slurry containing metal powder which may include a solder, water and a plasticizer rather than being extruded through an orifice prior to being sectioned, stacked, compacted, heated, sliced, and leached. In a still further form, sections are not formed, rather the continuous coated filament is wound onto a suitably shaped spool. The wound mass is then sintered to bond adjacent elements. The thusly formed mass is thereafter cut into thin slices which are normal to the axes of the original filament. Leaching is used to remove the filament pieces to create a porous plate.

United States Patent 1191 Sherfey June 3, 1975 PROCESS FOR MAKING SHEETS WITH PARALLEL PORES 0 UNIFORM IZE Primary ExaminerLeland A. Sebastian [75] Inventor: Joseph M. Sherfey, Lanham, Md. Agent or Flrm R' Kempf John [73] Assignee: The United States of America as represented by the United States [57] ABSTRACT 'Q f' AefonaunFs and Space Processes for making sheets with parallel pores of uni Admlmstratmn Offlce general form size are described. In one form, the process comcounsel'code washmgton prises the steps of: extruding a slurry formed of short, non-metallic filament pieces, a metal powder, water 22 i d; M 24, 1971 and a plasticizer through a suitable orifice to align the filament pieces parallel to one another; cutting the ex- [21] Appl. No.: 127,480 trusion into suitable sections; stacking the sections in parallel in a refractory container; compacting the 521 U.S. c1. 75/214; 29/1822; 29/1825; stack; heating the etaek in a reducing atmosphere;

29 4205; 5 3; 75 2 75 2 3 75 212; compacting while hot, if necessary; slicing, at right an- 75/222; 75/ 1; 161/92; 161/93; 117/12 gles to the longitudinal axis of the original sections, 117/12 GM the thusly formed billet into sheets; and, leaching out [51] Int. Cl B22f 5/00 the filament pieces in each sheet- In an alternate form, [58] Field of Search 75/DIG. 1, 212, 213, 214, a continuous filament, as pp to Short filament 75/200 222; 29/1322 1825 pieces, is used. In addition, the continuous filament is drawn through a slurry containing metal powder 56 References Ci which may include a solder, water and a plasticizer UNITED STATES PATENTS rather than being extruded through an orifice prior to being sectioned, stacked, compacted, heated, sliced, mgz zs 75/1) 1 and leached. In a still further form, sections are not 3218697 11/1965 waiger formed, rather the continuous coated filament is 3:282:658 11/1966 wainer wound onto a suitably shaped spool. The wound mass 3,313,622 4/1967 p is then sintered to bond adjacent elements. The thusly 3,322,535 5/1967 Rao formed mass is thereafter cut into thin slices which are 3,432,295 3/1969 Frank et a]. 75/DIG. 1 normal to the axes of the original filament. Leaching is OTHER PUBLICATIONS used to remove the filament pieces to create a porous plate.

25 Claims, 8 Drawing Figures CUT FILAMENTS FORM PASTE or cut FILAMENTS WATER,METAL mum rub PLASTICIZER EXTRUDE PASTE T0 ALIGN FILAMENTS OUT EXTRUSION TO FORM SECTIONS STACK SECTIONS COM FACT STACK HEAT SUCK IN REMING ATMOSPHERE TO FORM BILLET SLICE BILLET LEACH GJT FILAMENTS PATEHTEDJUH 3 I975 DRAW FILAMENT THROUGH METAL POWDER SLURREY CUT COATED FILAMENT STACK FILAMENTS COMPACT STACK HEAT STACK IN REDUCING ATMOSPHERE SLICE STACK LEACH OUT FILAMENTS HEET DRAW FILAMENT THROUGH METAL POWDER SLURREY WIND COATED FILAMENT ONTO SPOOL SINTER WOUND FILAMENT SLICE SINTERED MASS LEACH OUT FILAMENTS FIG. 7

INVENTORS JOSEPH M. SHERFEY ATTORNEYS PROCESS FOR MAKING SHEETS WITH PARALLEL PORES OF UNIFORM SIZE ORIGIN OF THE INVENTION The invention described herein was made by an employee of the United States Goverment and may be manufactured and used by or for the Goverment for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention is directed to porous metal sheets and more particularly to processes for making metal sheets with parallel pores of uniform size.

Porous plates or sheets are well known and widely used. In the past, they have been often used as sieves to separate fine particles from coarse particles. More recently, additional applications have been found for metal sheets of a porous nature. In particular, the field of electrochemistry has found applications for porous metal sheets. One such application is in the production of plaques that are used to form the electrodes of batteries. Plaques are porous sheets of metal that are impregnated with an active material to form plates. The active material is determined by the particular type of cell involved. For example, in the case of a nickel cadmium cell, the positive plate is formed by impregnating the pores of the plaque with nickel oxide and the negative plate is formed by impregnating the pores with cadmium oxide.

In general, prior art plaques have been made by sintering nickel powder onto a nickel screen or a perforated nickel sheet to form a highly porous rectangular structure of a predetermined thickness, such as 0.03 inches. The length and breadth of the porous plaques depend upon the size and type of the resultant cell.

Porous metal structures or plaques formed by sintering nickel powder onto a nickel screen are far from idea] because the pores of such plaques are widely distributed with respect to length, diameter, orientation and tortuosity. Only a fraction of the resultant pores reach the optimum with respect to these parameters. In fact, it has been found that as much as one half of the active material in plaques formed in this manner is electrochemically unavailable and polarization losses are unnecessarily high.

Because metal sheets with non-uniform pores are unsatisfactory for many such uses (e.g. sieves or plaques, for examples), the prior art has attempted to provide processes for making metal sheets with uniform pores of a small size. One such process starts with a rod formed of, for example, copper clad with another metal, such as nickel, for example. The rod is machined to obtain a billet having a square cross section. The billet is elongated by a suitable factor such as 81 and cut into suitable (81) equal length sections. The sections are reassembled into a 9 by 9 parallel array to form a new billet approximating the original size but containing 81 copper rods each one sized one-ninth its original size. This process is repeated one or more times to obtain the necessary reduction in the size of the copper rods. The billet is then cut perpendicular to the axes of the embedded copper rods to form sections. Porous sections are obtained by leaching the copper from solid sections.

While the foregoing process is an advance over the powder sintering process, it still has certain disadvanhave also been proposed. However, they have also been unsatisfactory for various reasons. One such approach stacks corrugated sheets in a pile with the grooves of all of the sheets running parallel. The pile is sintered to form a coherent mass and then sliced in a direction that is perpendicular to the grooves formed by the corrugations. One problem with this process lies in the diffi* culty of fabricating sheets with both a metal thickness and a corrugation depth in the thousandth-of-an-inch range. While this problem can be solved by means of electro-forming and other techniques, the handling of such material is a tedious, time consuming and expensive process. In addition, there is a tendency for the sheets to nest," thus obliterating some of the pores. Moreover, depending upon the thickness and strength of the materials involved, it is often necessary to fill the pores with wax or some other substance prior to slicing. This substance must later be removed by melting or by the application of some type of solvent.

Another prior art process for creating small pores in metal sheets involves the stacking of electro-formed screens. However, because small pore sizes are involved the difficulty of aligning the screens is acute. Hence, such processes have not been found effective for wide scale use. Another process utilizes a fiber pad with parallel outwardly projecting fibers. The voids between the fibers are filled with a metal powder which is subsequently solidified by mechanical compaction and/or sintering. The fabric skeleton is then burned off. While somewhat satisfactory, this process does not result in truly uniform pore sizes and locations due to the compressability of the pile fabric and the difficulty of orienting the outwardly projecting fibers into an exact array.

It can be seen from the foregoing brief synopsis of the prior art that no completely satisfactory process suit able for providing metal sheets having uniform pore sizes that are small and parallel has been developed by the prior art. This is particularly true when the pore sizes desired are in the thousandth-of-an-inch range in diameter.

Therefore, it is an object of this invention to provide new and improved processes for making metal sheets with parallel pores of uniform size.

It is also an object of this invention to provide new and improved processes for making porous metal sheets wherein the pores are small and uniform in size and wherein said process is uncomplicated and therefore suitable for widespread use.

It is a further object of this invention to provide processes for making porous metal sheets wherein the pores are uniform, parallel and in the thousandthof-an-inch range in diameter.

SUMMARY OF THE INVENTION It is known that various non-metallic filaments can be embedded in metal to form a composite structure. For i example, as set forth in US. Pat. No. 3,432,295 to Frank et al., short-length non-metallic filaments are mixed with a metal powder and water. The resultant paste is extruded through a small hole thus causing the filament to be aligned in a parallel array.

Alternately, as disclosed by William Kuhn of Spindletop Research, the filament can be essentially continuous and can be coated by being drawn through a slurry. The slurry contains a volatile liquid such as water or methanol and a powdered metal in a suspension and if necessary, other additives such as a thickener or suspending agent.

In accordance with principles of the present invention, such structures are formed in the foregoing or similar manners and are processed to form a metal sheet having small pores of uniform size. More specifically, in one form, a mixture of cut filaments, water, metal powder, and a plasticizer is extruded to form a paste material wherein the filaments are aligned. The extrusion is cut to form sections of equal length. The sections are stacked into a parallel array and compacted. After compacting, the stack is heated in a reducing atmosphere and. if necessary compacted again while hot to create a billet. The billet is then sliced into sheets, the slicing being performed at right angles to the longitudinal axes of the stacked sections. Thereafter, the filament pieces located in the sheets are leached out to create uniform size holes most of which extend through the sheets. In addition, interstitial pores formed between the sections may be included if the compacting step is not complete.

In accordance with alternate principles of this invention, the filament is continuous and is drawn through a slurry rather than extruded to form a wire like structure. The drawn filament with its coating is cut into equal length sections. The sections are stacked and compacted as before. The stack is then heated to form a billet which is sliced at right angles to the axes of the filament. The slices are leached to remove the filament pieces.

In accordance with still other principles of this invention, the filament after being drawn through the slurry and coated is wound onto a spool rather than being cut into sections. The spool-shaped mass is heated or sintered to form a spool-shaped billet. Thereafter, the billet created by the sintering operation is sliced at right angles to the direction of the filaments. Then, the filament pieces existing in the slices are leached out by a suitable reagent. Again, porous metal sheets having parallel pores of uniform size are created.

It will be appreciated from the foregoing brief summary of the invention that processes for creating metal sheets or plaques having small, parallel pores of uniform size are provided by the invention. Because the filaments are commercially available in small sizes, very small uniform holes may be induced into the sheet by the inventive process. Further, in addition to induced pores, interstitial pores can be provided by limiting the compacting step. It should be noted and it will be appreciated by those skilled in the art and others that a wide variety of metallic powders can be utilized by the inventive processes in combination with a wide variety of filaments, depending upon the desired nature of the resultant porous metal sheet or plaque.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram illustrating one process in accordance with the teachings of the invention;

FIG. 2 is a pictorial diagram illustrating an apparatus for carrying out a portion of the process set forth in FIG. 1',

FIG. 3 is a cross-sectional diagram illustrating an apparatus for carrying out another portion of the process set forth in FIG. 1;

FIG. 4 is a pictorial diagram illustrating another step in the process set forth in FIG. 1;

FIG. 5 is a block diagram illustrating an alternate process in accordance with the teachings of the invention;

FIG. 6 is a block diagram illustrating still another process in accordance with the teachings of the invention;

FIG. 7 is a pictorial diagram illustrating an apparatus for carrying out some of the steps of the process set forth in FIG. 6; and

FIG. 8 is a pictorial diagram illustrating a structure formed as a result of an intermediate step of the process set forth in FIG. 6.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 is a block diagram generally illustrating the various steps making up one process in accordance with the teachings of the invention. More specifically, short or cut filament wiskers or fibers are mixed with suitable ingredients such as metal powder, water and a plasticizer to form a paste. The paste is extruded through a small orifice to parallelize the fibers. The ex trusion is then cut into sections. The sections are stacked parallel in a suitable container and compacted while wet to remove any entrapped air. The wet compact is then further compacted while being heated in a reducing atmosphere to form a billet and the billet is sliced into sheets. The slicing takes place at right angles to the longitudinal axes of the filaments. The filaments are leached out of the sheet-like sections to form a porous sheet. The pores in the sheets are small, parallel, and uniform in size because the filaments are small, parallel arrayed and uniform in size.

Turning now to a more detailed description of the steps of the process illustrated in FIG. 1, the filament fibers may be formed of various materials. The filament fibers, for example, may be quartz monofilaments A inch long having a diameter of 0.001 inch. Alternatively, the filament fibers may be formed of a cheaper material, such as glass, for example. Still further, fibers could be formed from rayon or nylon. In general, the filament fibers may be formed of any thin wire-like material that is subject to removal by leaching the sheet with a suitable reagent. It will be appreciated by those skilled in the art that, in most cases, the choice of filament fibers will be determined by the fabrication processes involved and the ultimate use of the material.

In some cases the fibers may tent to clump together in the paste prior to or during extrusion. It will be appreciated that such clumping will prevent uniform sized pores form being created because the leaching of the fibers will leave a pore that is the size and shape of the clump. In order to prevent such oversized pores,

the fibers may be coated prior to incorporating them into the paste. For example, if nickel metal powder is to be used to form the porous sheet, the fibers may be coated with nickel prior to incorporation into the paste.

FIG. 2 is a pictorial diagram illustrating a structure for extruding the paste wherein as a result the chopped or cut fibers are arrayed in parallel. A cylindrical container 11 contains the paste 13 wherein the cut fibers are randomly oriented. A piston or plunger 15 fits into one end of the housing 11 and is forced inwardly by means of a rod 17. The other end of the cylindrical housing 11 is necked down by a suitable structure 19 to form a plurality of orifices or openings 21. If desired, the necking down could end in a single opening or a number of openings, such as three, as illustrated in FIG. 2. In any event, the paste extrusions 23 that exit from the openings are thin and elongated. The size of the openings can vary over a wide range. For example, the openings may be approximately /2 of an inch in diameter for a nickel metal powder slurry that includes filament fibers that are 4 inch long and 0.001 inch in diameter.

The extrusions 23 are cut into sections of equal length while the extrusions remain wet. As illustrated in FIG. 3, the sections 25 are stacked in parallel in a suitable container 27. The container is open at the top to allow a plate 29 to compact the stack under the action of a rod 31. Y

Compacting the sections 25,removes entrapped air from the container 27. After compacting, the stack is fired to create a billet. More specifically, preferably, the wet compact is first fired at a low temperature to remove water. and organic matter. Thereafter, the wet compact is fired at a higher temperature for a predetermined period of time to sinter the metal powder into a composite mass or billet. It will be appreciated that the exact low and high heating temperatures and the time of heating will vary in accordance with the actual paste composition. Also, it may be desirable to compact the mass while hot to increase density and strength. Preferably, the heating steps are performed in a reducting atmosphere. If, for example the metal powder is nickel the firing temperature will be about 900C and the period of time will be about 1 hour. In any event, as a result of the heating steps, water is evaporated, the plasticizer is burned off, and the powder is sintered into a co herent mass or billet.

It should be noted that the compacting step of this process can be performed hot or cold. It should also be noted and appreciated that complete compacting may neither be necessary nor desirable in some circumstances. If compacting is not complete, interstitial pores will be present and these may be desirable in some applications. Interstitial pores are voids of the type that are to be found in conventional sintered metal plaques. I I

As illustrated in FIG. 4, after the billet 33 has been at least partially compacted and sintered to increase its strength, it is sliced by any suitablemeans into thin sheets 35. The slicing isperformed perpendicular to the axes of the fibers. The fibers pieces appear in FIG. 4 as small circles 37 located on the surfaces of the sheets 35. After slicing, the fiber pieces are removed by leaching. For example, if the fiber pieces are quartz monofilaments they may be dissolved by leaching with hydrofluoric acid.

As noted above, if the process includes incomplete compaction a sheet having two kinds of pores-induced and interstitial-is formed. Induced pores are created when the filament pieces are removed. Interstitial pores are a result of the incomplete compaction of the pow dered metal matrix. The amount of porosity from each source is controllable. By controlling the extent of compaction, the amount of interstitial porosity is controlled and by controlling the diameter and number of the filament fibers, the size and number of the induced pores is controlled.

As previously stated, the details of the process and the exact nature of the materials involved can be varied over a wide range to meet the requirements of a specific application. The basic process can be used, for example, to produce sieves having holes smaller than any practical sieve currently available. For such a structure, it will be appreciated, that it is necessary to have essentially straight induced pores with smooth walls. Otherwise, clogging of the pores could be a problem. Straight smooth pores are easily obtainted by avoiding mechanical compaction and, instead, filling the interstitial pores with a braze prior to removal of the filament pieces.

It should be noted that if the filament fibers are coated before they are added to the slurry, a lined pore can be formed. For example, if silica fibers are coated with platinum and inserted into a nickel metal powder paste which is extruded and prepared in the manner previously described, platinum lined pores in a nickel sheet are created. More specifically, the extrusion thus formed is cut into sections of a suitable length, placed parallel in a a container, and then by means of suitable processing, including heating and compaction, formed into a sheet. Thus is obtained a metal sheet, free of voids, and containing a large number of non-metallic fibers, all parallel, and all having their axes essentially parallel to the face of the sheet.

The idea behind the present invention is to use the Frank process (U.S. Pat. No. 3,432,295), or any such process, to imbed filaments in a parallel array inside a metallic structure. This structure is then sliced perpendicular to the filament axes to form sheets with the filaments passing through the cut sections or slices from one face to the other. The filaments are then leached out of the slices to obtain the desired metal structure with parallel pores of uniform size.

FIG. 5 is a block diagram generally setting forth the steps of an alternate process formed in accordance with the teachings of the invention. In accordance with this process, the filament is continuous rather than cut into short lengths and is drawn through a metal powder slurry. As with the previously described process, the metal powder slurry generally includes a suitable metal powder, a wetting agent. water if needed, a thickner or plasticizer. If desired, the filament may be coated with a metal prior to passage through the metal powder slurry. This metal could be applied to the filament by sputtering. In any event, the slurry-coated monofilament, with or without additional processing such as drying and sintering can now be treated like the extruded material in the previously described process, i.e., cut into suitable lengths, compacted, sintered, sliced, leached, and dried. However, alternative approaches to a parallel pore structure are also possible. For example, the slurry-coated filament can be dried and then passed through a furnace where the metal powder coating is sintered. The coated filament is then wound onto a spindle, sintered to form a coherant mass, cut into slices that are perpendicular to the fibers, leached, washed, and dried.

In an especially attractive embodiment of the method employing a continuous filament, the slurry contains, in addition to the constituents mentioned above, a lowmelting metal or alloy such as cadmium or a lead-tin solder. The slurry-coated filament is treated as above, except that processing time is greatly reduced because the consolidation of the filament coating depends on the melting of the lowmelting metal or alloy instead of on sintering. In general, the time needed for such a melting process is a small fraction of that needed for sintering. If cadmium is employed as a binder it could be removed by evaporation at a later stage in the processing. Regardless of what metal is used as a binder or solder a final product free of interstitial porosity can be obtained by adding more binder or solder before the pore former is removed. As pointed out above, this consolidation technique obviates the need for mechanical compaction.

FIG. 6 generally illustrates, in block form, a further process formed in accordance with the teachings of the invention and briefly alluded to above. In accordance with the process illustrated in FIG. 6, a continuous filament is drawn through a metal powder slurry which forms a coating on the filament. Thereafter, the coated filament is wound upon a spool. These two steps are more clearly illustrated in FIG. 7 wherein a thin filament 41 from a coil source 43 passes through a slurry 45. After emerging from the slurry 45, the coated filament 47 is wound upon a spool 49.

While the spool 49 may be round, preferably, it is rectangular or oval in shape. In any event, after the filament spool mass reaches a predetermined size, the mass is sintered into a solid billet 51 (FIG. 8). Thereafter, the spool-shaped billet is sliced at right angles to the longitudinal axes of the filaments contained in the billet-such as along line AA illustrated in FIG. 8. The ressult is a more or less flat plate or sheet. The plates or sheets are now leached by a suitable reagent to remove the filament pieces whereby a porous plate or sheet is created.

It will be appreciated from the foregoing description that the last described process generally comprises the steps of: drawing a filament through a metal powder slurry; winding the coated filament onto a spool; sintering the wound filament; slicing the sintered mass; and leaching out the filament sections. If desired, after winding, the spool and windings can be compacted to reduce the size of or eliminate interstitial pores.

It will be appreciated by those skilled in the art and others that the invention provides novel processes for creating sheets with small, parallel and uniform pores. If desired, the sheets can be used as sieves in any conventional and well known manner. Alternatively, the sheets can be used as plaques in the formation of electrodes for batteries. Other uses will be apparent to those skilled in the art and others.

While the processes have been described as preferably including a nickel powder slurry, as previously stated, other types of powdered metal slurrys can also be used. In addition, other methods of coating the fila ment can be utilized by the invention. Further, the described processes can utilize materials other than metals in the slurry. For example, the processes use ceramic and plastic powders, if desired.

While preferred processes for carrying out the invention have been described, it will be appreciated by those skilled in the art and others that various changes can be made therein without departing from the scope of the invention. Hence, the invention can be practiced otherwise than as specifically described herein.

What is claimed is:

l. A process for making sheets with parallel pores of substantially uniform size comprising the steps of:

forming a plurality of longitudinal sections, said longitudinal sections comprising longitudinally arrayed filaments surrounded by a mixture including, in powdered form, the material of which said sheets are to be formed;

stacking said plurality of longitudinal sections with their longitudinal axes substantially in parallel; forming a billet of said plurality of stacked longitudinal sections;

slicing, to a predetermined sheet thickness, said billet at right angles to the longitudinal axes of the plurality of longitudinal sections making up said billet to form a sheet; and

removing said longitudinally arrayed filaments from the sheet.

2. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein the step of forming a plurality of longitudinal sections comprises the substeps of:

cutting a filament into a plurality of short fibers;

mixing said plurality of short fibers with other suitable materials, including, in powdered form, the material of which said sheets are to be formed, to

create a paste;

extruding said paste through at least one orifice to form a structure; and,

cutting said structure into said plurality of longitudinal sections.

3. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 2 wherein the step of forming a billet comprises the substeps of:

compacting said stack of longitudinal sections to eliminate at least some of the air trapped between said sections; and,

heating said compacted stack of longitudinal sections so as to form said billet.

4. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 3 wherein said heating substep is performed in a reducing atmosphere.

5. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 4 wherein said compacting step is complete and eliminates entirely all of the air trapped between said longitudinal sections.

6. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 5 wherein said paste consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.

7. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 6 wherein said powdered form of said material of which said sheets are to be formed is nickel powder.

8. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein the step of forming a billet comprises the substeps of:

compacting said stack of longitudinal sections to eliminate at least some of the air trapped between said sections; and,

heating said compacted stack of longitudinal sections so as to form said billet.

9. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 8 wherein said heating substep is performed in a reducing atmosphere.

10. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 8 wherein said compacting step is complete and elimi nates entirely all of the air trapped between said longitudinal sections.

11. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 10 wherein said mixture consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.

12. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein said step of forming a plurality of longitudinal sections comprises the substeps of:

drawing a continuous filament through a slurry, in

cluding, in powdered form, the material of which said sheets are to be formed, to coat said filament and create a structure; and,

cutting said structure into said plurality of longitudinal sections.

13. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 12 wherein the step of forming a billet comprises the substeps of:

compacting said stack oflongitudinal sectins to eliminate at least some of the air trapped between said sections; and,

heating said compacted stack oflongitudinal sections so as to form said billet.

14. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 13 wherein said heating substep is performed in a reducing atmosphere.

'15. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 14 wherein said compacting step is complete and eliminates entirely all of the air trapped between said longitudinal sections.

16. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 15 wherein said slurry consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.

17. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 16 wherein said powdered form of said material of which said sheets are to be formed is nickel powder.

18. A process for making sheets with parallel pores of substantially uniform size comprising the steps of:

drawing a continuous filament through a slurry, that includes, in powdered form, the material of which said sheet is to be formed, to coat said filament and create a structure;

winding said structure onto a spool;

forming a billet of said wound structure;

slicing said spool at right angles to the axes of said continuous filament winding to form a sheet having a plurality of filaments; and

removing said filaments from said sheet.

19. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 18 wherein the step of forming a billet comprises the substeps of:

compacting said wound structure to eliminate at least some of the air trapped between windings; and, heating said compacted wound structure so as to form said billet.

20. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 19 wherein said heating substep is performed in a reducing atmosphere.

2]. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 20 wherein said compacting step is complete and eliminates entirely all of the airtrapped between said winding.

22. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 21 wherein said slurry consists of the powdered form of said material of which said sheets are to be formed, a plasticizer, water, and a wetting agent.

23. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 22 wherein said powedered form of said material of which said sheets are to be formed is nickel powder.

24. The process of claim] wherein said filaments are nonmetalic and are removed from the sheets by leaching.

25. The process of claim 18 wherein said filaments are nonmetallic and are removed from the sheet by leaching. 

1. A PROCESS FOR MAKING SHEETS WITH PARALLEL PORES OF SUBSTANTIALLY UNIFORM SIZE COMPRISING THE STEPS OF: FORMING A PLURALITY OF LONGITUDINAL SECTIONS, SAID LONGITUDINAL SECTIONS COMPRISING LONGITUDINALLY ARRAYED FILAMENTS SURROUNDED BY A MIXTURE INCLUDING, IN POWDERED FORM, THE MATERIAL OF WHICH SAID SHEETS ARE TO BE FORMED; STACKING SAID PLURALITY OF LONGITUDINAL SECTIONS WITH THEIR LONGITUDINAL AXIS SUBSTANTIALLY IN PARALLEL; FORMING A BILLET OF SAID PLURALITY OF STACKED LONGITUDINAL SECTIONS; SLICING, TO A PREDETERMINED SHEET THICKNESS, SAID BILLET AT RIGHT ANGLES TO THE LONGITUDINAL AXES OF THE PLURALITY OF LONGITUDINAL SECTIONS MAKING UP SAID BILLET TO FORM A SHEET; AND
 1. A process for making sheets with parallel pores of substantially uniform size comprising the steps of: forming a plurality of longitudinal sections, said longitudinal sections comprising longitudinally arrayed filaments surrounded by a mixture including, in powdered form, the material of which said sheets are to be formed; stacking said plurality of longitudinal sections with their lingitudinal axes substantially in parallel; forming a billet of said plurality of stacked longitudinal sections; slicing, to a predetermined sheet thickness, said billet at right angles to the longitudinal axes of the plurality of longitudinal sections making up said billet to form a sheet; and removing said longitudinally arrayed filaments from the sheet.
 2. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein the step of forming a plurality of longitudinal sections comprises the substeps of: cutting a filament into a plurality of short fibers; mixing said plurality of short fibers with other suitable materials, including, in powdered form, the material of which said sheets are to be formed, to create a paste; extruding said paste through at least one orifice to form a structure; and, cutting said structure into said plurality of longitudinal sections.
 3. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 2 wherein the step of forming a billet comprises the substeps of: compacting said stack of longitudinal sections to eliminate at least some of the air trapped between said sections; and, heating said compacted stack of longitudinal sections so as to form said billet.
 4. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 3 wherein said heating substep is performed in a reducing atmosphere.
 5. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 4 wherein said compacting step is complete and eliminates entirely all of the air trapped between said longitudinal sections.
 6. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 5 wherein said paste consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.
 7. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 6 wherein said powdered form of said material of which said sheets are to be formed is nickel powder.
 8. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein the step of forming a billet comprises the substeps of: compacting said stack of longitudinal sections to eliminate at least some of the air trapped between said sections; and, heating said compacted stack of longitudinal sections so as to form said billet.
 9. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 8 wherein said heating substep is performed in a reducing atmosphere.
 10. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 8 wherein said compacting step is complete and eliminates entirely all of the air trapped between said longitudinal sections.
 11. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 10 wherein said mixture consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.
 12. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 1 wherein said step of forming a plurality of longitudinal sections comprises the substeps of: drawing a continuous filament through a slurry, including, in powdered form, the material of which said sheets are to be formed, to coat said filament and create a structure; and, cutting said structure into said plurality of longitudinal sections.
 13. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 12 wherein the step of forming a billet comprises the substeps of: compacting said stack of longitudinal sectins to eliminate at least some of the air trapped between said sections; and, heating said compacted stack of longitudinal sections so as to form said billet.
 14. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 13 wherein said heating substep is performed in a reducing atmosphere.
 15. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 14 wherein said compacting step is complete and eliminates entirely all of the air trapped between said longitudinal sections.
 16. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 15 wherein said slurry consists of the powdered form of said material of which said sheets are to be formed, said filament fibers, a plasticizer, water, and a wetting agent.
 17. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 16 wherein said powdered form of said material of which said sheets are to be formed is nickel powder.
 18. A process for making sheets with parallel pores of substantially uniform size comprising the steps of: drawing a continuous filament through a slurry, that includes, in powdered form, the material of which said sheet is to be formed, to coat said filament and create a structure; winding said structure onto a spool; forming a billet of said wound structure; slicing said spool at right angles to the axes of said continuous filament winding to form a sheet having a plurality of filaments; and removing said filaments from said sheet.
 19. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 18 wherein the step of forming a billet comprises the substeps of: compacting said wound structure to eliminate at least some of the air trapped between windings; and, heating said compacted wound structure so as to form said billet.
 20. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 19 wherein said heating substep is performed in a reducing atmosphere.
 21. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 20 wherein said compacting step is complete and eliminates entirely all of the air trapped between said winding.
 22. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 21 wherein said slurry consists of the powdered form of said material of which said sheets are to be formed, a plasticizer, water, and a wetting agent.
 23. A process for making sheets with parallel pores of substantially uniform size as claimed in claim 22 wherein said powedered form of said material of which said sheets are to be formed is nickel powder.
 24. The process of claim 1 wherein said filaments are nonmetalic and are removed from the sheets by leaching. 